Finasteride and dutasteride are oral medications that inhibit the 5-alpha reductase enzyme, reducing the conversion of testosterone into DHT.
Efficacy Comparison
Research shows a probable efficacy ranking of: dutasteride 0.5 mg/day > finasteride 5 mg/day > minoxidil 5 mg/day > finasteride 1 mg/day. Because dutasteride suppresses both Type 1 and Type 2 enzyme, it lowers serum DHT by roughly 98%, versus about 71% for finasteride (which targets Type 2 only).
Regulatory Status
Finasteride (1 mg/day) is the only 5-alpha reductase inhibitor FDA-approved for male AGA. Dutasteride is not yet approved for this indication in the US, but is approved at 0.5 mg/day in Japan and South Korea, and is widely prescribed off-label elsewhere.
Side Effects
Both drugs have been linked to sexual dysfunction (reduced libido, erectile difficulty) and, rarely, neuropsychiatric symptoms. These effects are usually reversible, though some users report persistence after discontinuation (post-finasteride syndrome is a documented, if debated, concern).